Random pulse generation

- British Nuclear Fuels PLC

A logic circuit monitors the outputs of R, F and T probability generators, provides an output pulse, and increments or decreases a counter, the output of which is fed back to the T probability generator. R represents the rate or frequency of a random background, F represents the fraction of events in the random background R that will have associated coincident pairs, and T a respective die-away time. The parameters R, F and T are decided by the user. Such a pulse generator may simulate the output from a neutron well, and may be used to test neutron coincidence systems in a simple and rigorous manner.

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Claims

1. A pulse generator comprising:

a first probability generator for generating a first output comprising a first pulse stream having pulses which are output with a first probability;
a second probability generator for generating a second output comprising a second pulse stream having pulses which are output with a second probability; and
a logic circuit for combining the outputs of said first and second probability generators and configured to produce an output pulse stream to simulate the output from a neutron well, the pulse stream having output pulses in dependence upon the states of the outputs of said probability generators;
wherein said first and second probability generators are designed to represent the values F and T respectively, wherein F represents the fraction of events in a random background that will have associated coincident pairs, and T represents a respective die-away time.

2. A pulse generator according to claim 1, further comprising a third probability generator for generating a third output comprising pulses which are output with a third probability, the logic circuit being arranged to combine the outputs of said first, second and third probability generators to produce an output pulse in dependence upon the states of the outputs of said probability generators.

3. A pulse generator according to claim 2, wherein said third probability generator is designed to represent the value R, wherein R represents the rate or frequency of the random background.

4. A pulse generator according to claim 3, including a counter for counting the number of output pulses of the pulse generator, which counter is incremented for each pulse representing a first of an associated coincident pair, and decreased for each pulse representing a second of the associated coincident pair, and an output of the counter is fed back to the third probability generator.

5. A pulse generator according to claim 3, further including a plurality of said second probability generators, wherein F represents the fraction of events in the random background that will have associated coincident triplets, quadruplets, or higher orders.

6. A pulse generator having an overall output and comprising:

a first probability generator for generating a first output, said first output comprising a pulse stream of pulses, said pulses being outputted with a first probability;
a second probability generator for generating a second output, said second output comprising a pulse stream of pulses, said pulses being outputted with a second probability;
a logic circuit receiving said first output and said second output, said logic circuit providing an overall output, a pulse in the first output resulting in a count pulse, said overall output comprising the pulse stream of the first output and one or more count pulses, the count pulses being spaced relative to the pulses of the first output according to the pulse stream of the second output.

7. A pulse generator according to claim 6, in which said overall output comprises a count pulse for each pulse in the first output.

8. A pulse generator according to claim 6 in which the pulses of the first output in the overall output equate to the first pulses of coincidence pulse pairs.

9. A pulse generator according to claim 6 in which the count pulses in the overall output equate to the second pulses of coincidence pulse pairs.

10. A pulse generator according to claim 6 in which the pulse stream of the second probability generator determines the spacing between the first and second pulses of coincidence pulse pairs, the spacing equating to time.

11. A pulse generator according to claim 6 in which the first probability relates to a mean frequency of coincidence pairs of pulses and the second probability relates to a die-away time.

12. A pulse generator according to claim 6, wherein at least one of said probability generators comprises first and second feed back shift registers, each register comprising a number of stages L, in each register an output of a first stage being bit m and an output of a second stage being bit n, said bits m and n forming inputs to a logic circuit, said logic circuit logically combining said bits m and n to form an output, the output of said logic circuit forming an input to the register from which said bits m and n were output, wherein L, m and n are different for said first and second registers, wherein a number of stages of said first register provide a number of outputs having x bits, a number of stages of said second register provide a number of outputs having x bits, and said x bits from said first register and said x bits from said second register form inputs to a comparator, and wherein said comparator provides the pulse output of the at least one of said probability generators.

13. A pulse generator according to claim 12 in which said logical combining comprises an exclusive-OR function.

14. A pulse generator according to claim 12 in which two or more of said probability generators comprise a pair of shift registers, the value of x being different for each probability generator.

15. A pulse generator according to claim 14 in which two or more of said probability generators share the same pair of feedback shift registers, but have a different respective comparator to provide a respective value of x which is different for each probability generator.

16. A pulse generator having an overall output and comprising:

a first probability generator for generating a first output, said first output comprising a pulse stream of pulses, said pulses being outputted with a first probability;
a second probability generator for generating a second output, said second output comprising a pulse stream of pulses, said pulses being outputted with a second probability;
a third probability generator for generating a third output, said third output comprising a pulse stream of pulses, said pulses being outputted with a third probability; and
a logic circuit receiving said first output, said second output and said third output, said logic circuit comparing the first and third outputs to determine coincident pulses there between, a coincident pulse resulting in a count pulse, said logical circuit providing said overall output, said overall output comprising the pulse stream of the third output and one or more count pulses, the count pulses being spaced relative to the pulses of the third output according to the pulse stream of the second output.

17. A pulse generator according to claim 16, in which said overall output comprises a count pulse for each coincident pulse between the first and third output.

18. A pulse generator according to claim 16 in which the coincident pulses of the first and third outputs equate to the first pulses of coincidence pulse pairs.

19. A pulse generator according to claim 16 in which the count pulses in the overall output equate to the second pulses of coincidence pulse pairs.

20. A pulse generator according to claim 16 in which the pulse stream of the second probability generator determines the spacing between the first and second pulses of coincident pulse pairs, the spacing equating to time.

21. A pulse generator according to claim 16 and designed to simulate the output from a neutron well, in which the first probability relates to the fraction of events in a random background that will give rise to coincident pairs, the second probability relates to the die away time and the third probability relates to the mean random background frequency.

22. A pulse generator according to claim 16, wherein at least one of said probability generators comprises first and second feed back shift registers, each register comprising a number of stages L, in each register an output of a first stage being bit m and an output of a second stare being bit n, said bits m and n forming inputs to a logic circuit, said logic circuit logically combining said bits m and n to form an output, the output of said logic circuit forming an input to the register from which said bits m and n were output, wherein L, m and n are different for said first and second registers, wherein a number of stages of said first register provide a number of outputs having x bits, a number of stages of said second register provide a number of outputs having x bits, and said x bits from said first register and said x bits from said second register form inputs to a comparator, and wherein said comparator provides the pulse output of the at least one of said probability generators.

23. A pulse generator according to claim 22 in which said logical combining comprises an exclusive-OR function.

24. A pulse generator according to claim 22 in which two or more of said probability generators comprise a pair of shift registers, the value of x being different for each probability generator.

25. A pulse generator according to claim 24 in which two or more of said probability generators share the same pair of feedback shift registers, but have a different respective comparator to provide a respective value of x which is different for each probability generator.

26. A pulse generator according to claim 16, including a counter for counting output pulses of the pulse generator, which count is incremented for each pulse representing the first of a pair of coincident pulses and is decreased for each pulse representing the second of a pair of coincident pulses, the output of the counter being fed back to the second probability generator to control the respective number of x for that generator.

27. A pulse generator according to claim 26 in which the output from the counter varies with the balance of the counter, the higher the balance, the higher the value of x.

28. A method of testing a neutron coincidence system, comprising: generating a series of pulses forming a total output by means of one or more pulse generators, said total output being the combined overall output(s) of said one or more generators, wherein at least one of said pulse generators comprises a pulse generator having an overall output and comprising:

a first probability generator for generating a first output, said first output comprising a pulse stream of pulses, said pulses being outputted with a first probability;
a second probability generator for generating a second output, said second output comprising a pulse stream of pulses, said pulses being outputted with a second probability; and
a logic circuit receiving said first output and said second output, said logic circuit providing an overall output, a pulse in the first output resulting in a count pulse, said overall output comprising the pulse stream of the first output and one or more count pulses, the count pulses being spaced relative to the pulses of the first output according to the pulse stream of the second output; said total output simulating the output of a neutron well and forming an input for a neutron coincidence system.
Referenced Cited
U.S. Patent Documents
3790768 February 1974 Chevalier et al.
3946215 March 23, 1976 May
4173000 October 30, 1979 Singer et al.
4951243 August 21, 1990 Tomlinson, Jr.
5153532 October 6, 1992 Albers et al.
5175798 December 29, 1992 Taylor et al.
Foreign Patent Documents
0 113 181 A1 July 1984 EPX
1 322 915 July 1973 GBX
1 517 274 July 1978 GBX
Other references
  • Lightfoot, J.A., et al., A Computer Controlled, High Performance, Neutron Coincidence Counting System, Nuclear Instruments and Methods in Physics Research, A271, 636-643, (1988).
Patent History
Patent number: 5841680
Type: Grant
Filed: Jul 28, 1995
Date of Patent: Nov 24, 1998
Assignee: British Nuclear Fuels PLC (Cheshire)
Inventor: John Adrian Lightfoot (Cumbria)
Primary Examiner: David H. Malzahn
Law Firm: Fish & Richardson, P.C.
Application Number: 8/508,812
Classifications
Current U.S. Class: 364/71703
International Classification: G06F 102;